Drain and rinse marrowfat peas, then simmer covered in 600ml water for 30 minutes until tender.
Evaporate excess water, then mix in butter and lemon juice and season with salt and pepper.
Whisk yeast, sugar, beer, vinegar, flour, and salt in a bowl until combined.
Leave the batter to ferment until it begins to bubble.
Stir chopped dill into the fermented batter.
Heat vegetable oil in a heavy frying pan until a breadcrumb sizzles.
Coat cod in batter and fry for 5 minutes until golden, then drain and season.
Whisk olive oil and lemon juice together to dress the pea shoots.
Plate the mushy peas topped with fish and dressed pea shoots.